This mesh is a part of a polar mesh bounding by two radius and two angles. It is defined by a num_r * num_t matrix of points describing num_t-1 angular sectors and num_r concentric arcs of circle. The mesh is structured as following:
num_r Number of concentric circles
num_t Number of angles
r Array of num_r radius of the circles. This array may follow the rule :
r[i] < r[i+1] [forall] i, 0<=i<=num_r -2
t Array of num_t angles (in radian). This array may follow the rule:
t[j] < t[j+1] [forall] j, 0<=j<=num_t -2
0 <= t[j] <= 2[pi] [forall] j, 0<=j<=num_t -1
s Matrix of num_r * num_t values, one for each mesh node. These values are used to color the mesh depending on contouring values.
v Matrix of num_r * num_t vectors, one for each node of the mesh
